does the choke affect the sound of an amp?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Chi, Feb 25, 2005.


  1. Chi

    Chi Member

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    Howdy-
    Got a question for the tech guru's on the board. I have a vintage Vox AC-30 and turns out that the original Woden choke has to be rewound due to some winding damage. Mercury Magnetics will be doing the rewinding.

    Will this effect the tone of the amp much/at all? From what I am told by a few people in the know, the choke is more of a "filtering" device in an amp, it would NOT change things as drastically as say, replacing the OT or PT. Mercury is the best out there from what I'm told when it comes to these types of things....

    I just want the amp to sound as close to original as possible...any advice/suggestions would be great.

    Thanks in advance...
     
  2. Andy H.

    Andy H. Member

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    I had a choke in my Orange 120 head go microphonic some years back. The amp was blowing up caps occasionally, no obvious reason. We traced it eventually to the choke putting out nasty voltage spikes. Ran the amp for quite a while with just an 80 ohm resistor instead, and it sounded fine. A little hum, but nothing drastic - I think those amps are pretty well sorted anyway. Eventually John P. put in another choke for me, probably trawled out of some 'donor' Marshall or some such knowing him. ;)

    Anyway, no great tonal effect with my amp, just as you say a bit of hum filtering. My guess is you'll be quite happy with your rewind from MM.

    Andy.
     
  3. John Phillips

    John Phillips Member

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    Probably a Sound City or something like that :). They often used Partridge components too.

    I doubt the precise characteristics of the choke have a significant effect on the tone. It's not in the direct signal path - it supplies current to the lower stages of the B+ chain, and the feed for the OT comes before it in almost all guitar amp designs. The current through it should be pretty constant - it's not affected by the changing current to the power tubes, although the screen-grid feed is usually from the output side of it, and that does vary slightly.

    As long as it's rewound to the correct inductance and DC resistance, it should be fine.
     
  4. Andy H.

    Andy H. Member

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    Good stuff John! :cool:

    When you say 'too', were you referring to Orange using Partridges at times? I know that SC and Hiwatt did, but have never been sure what Orange were using in the '70s. (Not that that would change my high opinion of my 120 anyway, but interested nonetheless!)

    Andy.
     
  5. Jon Silberman

    Jon Silberman 10Q Jerry & Dickey Gold Supporting Member

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    I have always wondered about what exactly it is a choke does, some of that is answered here, but why is it a "choke," what does it "choke," hum? But if so, what is causing the hum?

    Also, over on the Traynor group, the earliest YBA-1s seem to be the most sought after and everyone always specifically refers to "the models with the choke, not the resistor." Why is that if the choke shouldn't impact the tone much anyway (or should it)?
     

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